Understand the idea.
The situation matters
A need is something required for a purpose or for living safely and well. A want is something someone would enjoy but can do without in the stated situation. Ask what the person must be able to do.
The same item can matter differently to different people. A ticket may be needed when a child must travel by bus, but not when that child can walk safely. Explain the situation without judging the person.
Use a budget to choose
A budget is the money available for a plan. Find the cost of the things that must be bought first. Subtract those costs before deciding whether any optional purchase fits.
A useful choice needs a reason as well as a calculation. Check that it meets the stated need and stays within the budget. More than one plan may work when several choices satisfy both conditions.
| Choice | Cost |
|---|---|
| Required bus ticket | 5 dollars |
| Fruit to go with a packed lunch | 2 dollars |
| Optional souvenir sticker | 3 dollars |
See the method in action.
Meet the stated need
For the outing above, a child must buy the bus ticket and has 7 dollars. Can they also buy the 3-dollar sticker?
Worked solution
- 1
Pay for the required ticket first.
The bus ticket must be included before choosing anything optional.
- 2
Compare the sticker with the money left.
A three-dollar sticker costs more than the remaining two dollars.
- 3
Check the full proposed cost.
Eight dollars is above the seven-dollar budget, so both purchases do not fit.
No. The sticker does not fit this budget after the ticket.
Explain a different situation
A student needs a pencil for class. A plain pencil costs 50 cents and a decorated pencil costs 2 dollars. The budget is 1 dollar. Suggest a plan.
Worked solution
- 1
Identify what the pencil must do.
Either pencil can meet the stated need to write in class.
- 2
Compare both prices with the budget.
One dollar is 100 cents; only the plain pencil is affordable.
- 3
Buy the plain pencil and find the remainder.
This plan meets the writing need and keeps the spending within the budget.
Buy the plain pencil and keep 50 cents.
Try it yourself.
Check your understanding
A required ticket costs 4 dollars. You have 6 dollars. An optional toy costs 3 dollars. Can you buy both?
Show answer & reasoning
No.
Together the ticket and toy cost dollars. This is dollar more than the budget, so you cannot buy both.
Keep practising
6 worksheet questions
Read the questions online
- A child has lunch packed but needs a 2-dollar bus ticket to reach the outing. Which is the stated need: the ticket or an optional badge?
- You have 5 dollars. A required workbook costs 3 dollars. How much remains?
- Using the previous budget, can you also buy a 3-dollar sticker set? Explain.
- A required pencil costs 60 cents. You have 1 dollar. Choose either a 20-cent sticker or a 50-cent eraser as an extra. Give an affordable plan.
- One child needs shoes for sport. Another already has suitable shoes. Explain why buying shoes could be a different priority for them.
- You must spend 4 dollars on materials and have 8 dollars. Suggest a reasonable use for the remaining 4 dollars and explain it.
Read the worked solutions
- A child has lunch packed but needs a 2-dollar bus ticket to reach the outing. Which is the stated need: the ticket or an optional badge?
The ticket is required for travel in this situation; the badge is optional.
The bus ticket. - You have 5 dollars. A required workbook costs 3 dollars. How much remains?
.
2 dollars. - Using the previous budget, can you also buy a 3-dollar sticker set? Explain.
dollars, above the 5-dollar budget.
No. Only 2 dollars remain, so it is 1 dollar short. - A required pencil costs 60 cents. You have 1 dollar. Choose either a 20-cent sticker or a 50-cent eraser as an extra. Give an affordable plan.
cents. The pencil and eraser would cost 110 cents, too much.
The pencil and sticker cost 80 cents and leave 20 cents. - One child needs shoes for sport. Another already has suitable shoes. Explain why buying shoes could be a different priority for them.
Use the different situations; no single purchase priority fits everyone.
The first child may need shoes to take part safely. The second may not need another pair now. - You must spend 4 dollars on materials and have 8 dollars. Suggest a reasonable use for the remaining 4 dollars and explain it.
dollars remain. Another clearly explained affordable choice is acceptable.
For example, save the remaining 4 dollars for the next materials purchase.
Curriculum reference & lesson scope
Australian Curriculum v9 and SA Curriculum Mathematics
Dollars/cents; equivalent amounts; modelling purchases; needs/wants; class enterprise and others' wellbeing.
Official curriculum source ↗